import assert from "node:assert/strict";
import { readFileSync } from "node:fs";
import test from "node:test";
import { createElement } from "react";
import { renderToString } from "react-dom/server";

import { StreamingMarkdown } from "../src/components/chat-message-content.tsx";
import { splitStableMarkdown } from "../src/lib/chat-markdown-split.ts";

const contentSource = readFileSync(new URL("../src/components/chat-message-content.tsx", import.meta.url), "utf8");
const messageRowSource = readFileSync(new URL("../src/components/chat-message-row.tsx", import.meta.url), "utf8");

test("the stable prefix ends at the last completed paragraph and the tail keeps streaming", () => {
  assert.deepEqual(splitStableMarkdown("只有一段还没写完"), { stable: "", tail: "只有一段还没写完" });
  assert.deepEqual(splitStableMarkdown("第一段。\n\n第二段还在"), { stable: "第一段。", tail: "第二段还在" });
  assert.deepEqual(
    splitStableMarkdown("## 标题\n\n第一段。\n\n第二段。\n\n第三"),
    { stable: "## 标题\n\n第一段。\n\n第二段。", tail: "第三" },
  );
});

test("the cut never lands inside a fence, between list items, or inside a table", () => {
  const fenced = "前言。\n\n```txt\n第一行\n\n第二行";
  assert.deepEqual(splitStableMarkdown(fenced), { stable: "前言。", tail: "```txt\n第一行\n\n第二行" });

  const looseList = "- 甲\n\n- 乙\n\n- 丙还在";
  assert.deepEqual(splitStableMarkdown(looseList), { stable: "", tail: looseList });

  const listThenParagraph = "- 甲\n- 乙\n\n总结一下";
  assert.deepEqual(splitStableMarkdown(listThenParagraph), { stable: "- 甲\n- 乙", tail: "总结一下" });

  const orderedListContinues = "1. 甲\n\n2. 乙\n\n   缩进的补充";
  assert.deepEqual(splitStableMarkdown(orderedListContinues), { stable: "", tail: orderedListContinues });

  const table = "说明。\n\n| 技法 | 状态 |\n| --- | --- |\n| 甲 | 已执行 |\n\n> 引用";
  assert.deepEqual(
    splitStableMarkdown(table),
    { stable: "说明。\n\n| 技法 | 状态 |\n| --- | --- |\n| 甲 | 已执行 |", tail: "> 引用" },
  );
});

test("growing the tail keeps the prefix string identical so the memoised prefix is not re-parsed", () => {
  const before = splitStableMarkdown("第一段。\n\n第二段。\n\n第三段正在");
  const after = splitStableMarkdown("第一段。\n\n第二段。\n\n第三段正在写，还没有换段");
  assert.equal(before.stable, after.stable);
  assert.notEqual(before.tail, after.tail);

  // Only once a new paragraph completes does the prefix move forward.
  const later = splitStableMarkdown("第一段。\n\n第二段。\n\n第三段写完了。\n\n第四");
  assert.equal(later.stable, "第一段。\n\n第二段。\n\n第三段写完了。");
});

test("the streaming renderer parses the prefix and the tail as two separate documents", () => {
  const calls: string[] = [];
  const renderMarkdown = (text: string) => {
    calls.push(text);
    return createElement("p", null, text);
  };
  renderToString(createElement(StreamingMarkdown, {
    text: "第一段。\n\n第二段。\n\n第三段还在",
    renderMarkdown,
  }));
  // Server rendering evaluates the tail in the parent and the memoised prefix as a child,
  // so compare as a set: what matters is that neither call sees the whole answer.
  assert.deepEqual([...calls].sort(), ["第一段。\n\n第二段。", "第三段还在"].sort());

  // The prefix component is memoised on its text, so an unchanged prefix costs no parse.
  assert.match(contentSource, /const StableMarkdownPrefix = memo\(function StableMarkdownPrefix/);
  assert.match(contentSource, /splitStableMarkdown\(text\)/);
  assert.match(contentSource, /streaming\s*\?\s*<StreamingMarkdown/);
  // Settled answers still parse once as one document.
  assert.match(contentSource, /: renderMarkdown\s*\?\s*renderMarkdown\(spoken\)/);
  assert.match(messageRowSource, /streaming=\{message\.state !== "settled"\}/);
});